Hydraulic bale wrapper

ABSTRACT

Apparatus for wrapping an article in a film (e.g. a plastics film) comprises a pair of stretch rollers for stretching the film, a film dispenser for delivering the film to the stretch rollers and means for rotating the article to take up stretched film from the stretch rollers, wherein the means for rotating the article comprises a first hydraulic motor and the stretch rollers are driven by a second hydraulic motor connected in series to the first motor to run on the exhaust from the first motor, whereby the ratio of the output of the first and second motors is fixed. One of the pair of stretch rollers constitutes the first of two nipped rollers, the second nipped roller being directly driven by the second motor and geared to the first nipped roller to drive it at the same peripheral velocity. The apparatus may be used for wrapping bales of silage.

This invention is concerned with apparatus for and a method of wrappingarticles in film, and in particular for wrapping bales of silage inplastic film.

BACKGROUND TO THE INVENTION

It is common practice to wrap bales of silage in plastics film suppliedin rolls. This helps to preserve the silage in the period between beingcut and being used as animal fodder.

An important consideration in wrapping practice is the speed ofwrapping, and it is desirable to wrap as quickly as possible while usingthe largest standard (i.e. readily available) width of film.

Other considerations are the ease of control and maintenance costs.

Apparatus for wrapping pallets loaded with goods are known in the art,and such apparatus commonly employs electric motors to rotate the bundleand to provide stretched plastic film via a pair of driven stretchrollers. In such apparatus it is important that the speed of rotation ofthe bundle relative to the speeds of rotation of the stretch rollers areaccurately maintained. This prevents overrun and excessive stretching orthe development of slack in the film. Excessive stretching can lead to"necking" in the film, which can result in uneven coverage of the palletor article to be wrapped. If such apparatus were used for wrappingsilage, uneven coverage could lead to spoilage.

However, electrical control systems for accurately and reliablymonitoring and regulating the relative speeds of rotation of the articleor bundle and the stretch rollers are expensive and difficult tomaintain. These disadvantages are exacerbated when high wrapping speedsare required, when even small differences in the relative rotationalspeeds of the bundle and stretch rollers can lead to overrun andexcessive stretching or the development of slack. In such circumstancesthe electrical control equipment is expensive, difficult to maintain andcomplicated to operate.

EP-A-0 096 635 discloses method and apparatus for wrapping palletisedgoods. Film from a roll is drawn around two rollers driven by two motorsand prestretched by these rollers before it is applied to the loadlocated on a turntable T driven by a third motor. Between the tensioningor stretching rollers and the load there is a resiliently-supportedroller whose position is a function of the film tension. Its position isfollowed by a tension sensor which feeds a signal to a servo controller.The servo controller governs the speeds of one or more of the motors toensure the film stretch is kept below the rupture elongation.

FR-A-2 639 023 discloses a film wrapping system having a turntable forthe load to be wrapped, which is rotated by a motor. Film is supplied tothe load from a supply roll via a roller which is driven by a secondmotor. For stretching the film, and instead of using a brake system, thetwo motors are driven such that the speed of turntable motor is alwaysgreater than film-delivery motor. The motors are electric motors, forexample variable speed motors.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improvedapparatus for and method of wrapping articles.

It is a further object of the invention to provide a simple and reliableapparatus for and method of wrapping articles at high speeds.

The present invention provides apparatus for wrapping an article in afilm (e.g. a plastics film), comprising a pair of stretch rollers forstretching the film, a film dispenser for delivering the film to thestretch rollers and means for rotating the article to take up stretchedfilm from the stretch rollers, wherein the means for rotating thearticle comprises a first hydraulic motor and the stretch rollers aredriven by a second hydraulic motor connected in series to the firstmotor to run on the exhaust from the first motor, whereby the ratio ofthe output of the first and second motors is fixed.

In another aspect the invention provides a method of wrapping an articlein film (eg. a plastics film), comprising the stop of feeding the filmfrom a dispenser to the article via a pair of stretch rollers whilerotating the article by means of a first hydraulic motor, wherein thestretch rollers are driven by a second hydraulic motor connected inseries to the first motor to run on the exhaust from the first motor,whereby the ratio of the output of the first and second motors is fixed.

Thus in the apparatus and method of the invention, the relative speedsof rotation of the bundle and the stretch rollers is accurately andsimply maintained by employing a first hydraulic motor to drive thebundle and driving the stretch rollers with a second hydraulic motorcoupled in series with the first motor to run on the exhaust of thehydraulic motor. In this way the rotation of the bundle and the stretchrollers are effectively coupled so that the ratio of the output of thefirst and second motors is fixed.

BRIEF DESCRIPTION OF THE INVENTION

An embodiment of the present invention will now be described by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic plan view of apparatus according to the presentinvention for wrapping a bale of silage in plastics film, and

FIG. 2 is a circuit diagram showing the arrangement of the hydraulicmotors as used in the apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a bale of silage 14 is mounted on aturntable (not shown) driven by motor 20. The turntable may be driven atup to speeds of 100 r.p.m., though speeds of 60 r.p.m. are normallypreferred.

The turntable may have a pair of rollers rotatable about theirlongitudinal axes so that the bale 14 can be rotated about the turntableaxis and simultaneously about its own axis on the turntable rollers.

A film dispenser 2 feeds a roll of film 4 to rollers 6,8 and 12. Rollers6 and 8 are nipped, and roller 6 is driven by a hydraulic motor 22.Rollers 6 and 8 are geared to run at the same peripheral velocity, andtogether act to isolate the dispenser 2 from fluctuations in tension inthe film arising from variations in the shape of the bale 14.

Rollers 8 and 12 act together as stretch rollers, roller 12 runningfaster than roller 8 which is geared to the other stretch roller 6 todrive it at, for example, a 55% to 70% higher peripheral velocity. Thefilm 10 passing between rollers 8 and 12 is therefore stretched.

The film is taken up by the bale 14 in the stretched state, and tomaintain the film in the stretched state after it leaves the roller 12 abiased jockey (not shown) may be incorporated to maintain the tension inthe film 16 passing between roller 12 and bale 14.

The turntable motor 20 and the stretch roller motor 22 are coupled inseries by hydraulic hosing 30. The hosing is preferably 0.5 or 0.75 inch(12.7 or 19 mm) bore. Oil is introduced under pressure at the inlet 26and is returned via the return at 28. The hose is preferably capable ofwithstanding oil pressures of up to 3000 psi (207 bar).

The coupling between the motors is regulated by a flow control valve 24,which draws off part of the exhaust oil leaving motor 20. Adjustment ofthe flow control valve 24 permits coupling of the outputs of motors 20and 22 such that they are effectively coupled.

The circuit may incorporate valves. The valves may act simply as safetyvalves to prevent overpressure of the motors, but may also be arrangedto permit operation of the motors in reverse direction. Such anarrangement may be useful where it is desired to reverse the directionof the turntable. Such reversal may be required after wrapping iscompleted when the bales can be oriented in a particular way to allowremoval from the turntable or automatic ejection e.g by a turntabletilting mechanism.

INDUSTRIAL APPLICABILITY

The invention is applicable to the wrapping of objects with a stretchedwrapping film, more particularly to the wrapping of agriculturalproducts. The invention is especially suited for the wrapping of bundlesof silage.

I claim:
 1. Apparatus for wrapping an article in a film (e.g. a plasticsfilm), comprising a pair of stretch rollers for stretching the film, afilm dispenser for delivering the film to the stretch rollers and meansfor rotating the article to take up stretched film from the stretchrollers, wherein the means for rotating the article comprises a firsthydraulic motor and the stretch rollers are driven by a second hydraulicmotor connected in series to the first motor, whereby the ratio of theoutput of the first and second motors is regulated by a flow controlvalve which controls fluid flow from the first hydraulic motor to thesecond hydraulic motor.
 2. Apparatus according to claim 1 wherein one ofthe pair of stretch rollers constitutes the first of two nipped rollers,the second nipped roller being directly driven by the second motor andgeared to the first nipped roller to drive it at the same peripheralvelocity.
 3. Apparatus according to claim 2 wherein the stretch rollerwhich constitutes the first of the two nipped rollers is geared to theother stretch roller to drive it at a 55% to 70% higher peripheralvelocity.
 4. Apparatus according to claim 1 wherein the flow controlvalve is arranged to be able to bleed off part of the exhaust fluid fromthe first motor.
 5. Apparatus according to claim 1, further comprising abiased jockey which maintains tension in the film between the articleand the stretch rollers.
 6. Apparatus according to claim 1 wherein thearticle is a bale of silage.
 7. A method of wrapping an article in film(e.g. a plastics film), comprising the step of feeding the film from adispenser to the article via a pair of stretch rollers while rotatingthe article by means of a first hydraulic motor, wherein the stretchrollers are driven by a second hydraulic motor connected in series tothe first motor, whereby the ratio of the output of the first and secondmotors is regulated by a flow control valve which controls fluid flowfrom the first hydraulic motor to the second hydraulic motor.
 8. Amethod according to claim 7 wherein one of the pair of stretch rollersconstitutes the first of two nipped rollers, the second nipped rollerbeing directly driven by the second motor and geared to the first nippedroller to drive it at the same peripheral velocity.
 9. A methodaccording to claim 8 wherein the stretch roller which constitutes thefirst of the two nipped rollers is geared to the other stretch roller todrive it at a 55% to 70% higher peripheral velocity.
 10. A methodaccording to claims 7 or 8 further comprising the step of employing theflow control valve to bleed off part of the exhaust fluid from the firstmotor.
 11. A method according to claim 7 wherein the method furthercomprises maintaining tension in the film between the article and thestretch rollers with a biased jockey.
 12. A method according to claim 7,wherein in the article is a bale of silage.